Room temperature transport measurements of a gated graphene monolayer, whose field effect is tuned by an oxide backgate and an electrochemical gate, are presented. The graphene samples are obtained by mechanical exfoliation, and conductance as a function of gate voltage and molarity of the electrochemical solution is measured. The experimental data are then explained and fit by a transport theory using Rode's method and incorporating several scattering mechanisms such as acoustic phonon, optical phonon, remote impurity, and surface roughness scattering. The calculation shows impurity scattering and roughness scattering to be very important scattering mechanisms for room temperature graphene transport. Moreover, the disorder in graphene raises the value of minimum conductivity from the reported theoretical minimum.